Service manual

ALIGNMENT AND TEST PROCEDURES
7-2
Month 2000
Part No. 001-2004-601
7.1.4 RECEIVER FREQUENCY ADJUST
1. Place a pick-up loop (sniffer) or RF probe con-
nected to a frequency counter near L139.
2. Set Y401 (TCXO) for the Injection Frequency
±50 Hz (Inj Freq = chnl freq + 52.95 MHz).
7.1.5 VCO TEST
1. The software programs the synthesizer for
1 MHz above the receive channel.
2. The voltage on TP401 should be < 10V.
3. Record the voltage on TP101 __________.
4. The software programs the synthesizer for
1 MHz below the receive channel.
5. The voltage on TP401 should be > 4V.
6. Record the voltage on TP101 __________.
7. If the voltages recorded in Steps 3 and 6 are not
within ±0.2V, tune L141 as required to balance the
voltage readings.
8. The software programs the synthesizer for the
receive frequency.
7.1.6 FRONT END ADJUSTMENTS
NOTE: Verify that the appropriate IF jumpers (J203,
J204, J205) are selected.
1. Set the signal generator to the receive frequency at
a level sufficient to produce an output voltage at
TP201 or J201, pin 7 (RSSI Output).
2. Tune L102, L103, L104, L108, L109 and L110,
then repeat, for a peak voltage at TP201. Decrease
the generator output level to maintain a
2-3V reading at TP201.
FOR 12.5 kHz CHANNELS:
NOTE: Perform this test if C239 and C249 are placed
on the board.
1. Set the generator to an RF level sufficient to pro-
duce 2V DC at TP201.
2. Remove any modulation from the signal generator.
3. Increase the signal generator RF frequency 2.5 kHz.
4. Adjust C239 for peak DC voltage at TP201.
5. Adjust C249 for peak DC voltage at TP201.
6. Reset the signal generator to the tune-up frequency.
7. Set the signal generator to 100 µV into the receiver
with a 1 kHz tone at ±1.5 kHz deviation.
(1000 µV at the generator with 20 dB pad gives
100 µV at the receive antenna.)
8. Tune Z215 for 2V ±0.05V at U203, pin 9.
9. Tune R253 for 387 mV RMS, ±5 mV RMS, at
TP202.
10.Adjust R248 for 2V ±0.05V at TP202.
11.Connect a distortion analyzer to TP202.
12.Tune L211, L213, L214 and L216 for minimum
distortion <5%, (typically <3%).
13.Repeat Step 12 then Steps 8, 9 and 10.
7.1.7 AUDIO DISTORTION
1. Plug a 16 ohm load at J101 or J104 on the MAC
(Main Audio Card).
2. Connect a distortion analyzer to the 16 ohm load.
3. Measure the distortion of the receive audio at J101
or J104 on the MAC with the local volume control
set to 2.8V RMS.
4. The reading shall be less than 3%.
(Typically less than 1%.)
5. Measure receive sensitivity at J101 or J104 on the
MAC.
6. The reading should be less than 0.35 µV.
(Typically 0.25 µV.)